Did you see the ring around the moon last night? If you did and wondered what caused it, Yahoo! Buzz Log has the answer:

Though it looked ominous, the shiny ring around the moon last night was actually a rather common weather phenomenon. According to various weather-related blogs across the Buzz, this ring around the moon occurs when thin cirrus clouds, which contain ice crystals, refract the moonlight. A blog from the Goddard Space Flight Center explains that "the shape of the ice crystals results in a focusing of the light into a ring. Since the ice crystals typically have the same shape, namely a hexagonal shape, the Moon ring is always the same size."